Direct injection is a common type of fuel injection system in which fuel is injected directly into the combustion chambers of an internal combustion engine by fuel injectors. A fuel rail, typically a tubular member, connects the fuel injectors to a fuel supply. Fuel injectors are typically mounted in fuel injector sockets in the fuel rail. Fuel rails in direct injection fuel systems are commonly mounted on the engine's cylinder head.
Direct injection fuel rails experience significantly higher fuel pressures than other types of fuel injection systems. High-pressure fuel pumps used in these systems commonly create pressure pulsations that can cause the fuel rail to vibrate. This can create undesirable noise, especially noticeable at idle speeds. Forces originating from the structure of fuel injectors can also cause undesirable noise, such as that caused by the energizing of magnetic solenoid valves and the impact of injector pins seating at injector closing. These fuel rail and injector noises travel directly to the cylinder head on which the fuel rail is mounted, and from there to other engine components such as the oil pan, front cover, cam cover, and intake manifold.
Attempts to alleviate noise problems have included the use of elastomeric washers or O-rings in the fuel rail mounting assembly to dampen vibrations. However, it is difficult to control vibration frequencies with elastomeric components. In addition, elastomers are subject to relatively rapid wear which can change the elastomeric characteristics.
A simple fuel rail mounting assembly is needed that can support relatively high fuel pressure and combustion pressure loads while reducing engine noise.